[0001] The present invention relates to a vehicle height control apparatus, and more particularly
to a vehicle height control apparatus of the type which includes a plurality of fluid
actuators disposed between a body structure of a wheeled vehicle and a plurality of
road wheels for controlling each vehicle height at the road wheels to a predetermined
vehicle height.
[0002] In Japanese Patent Laid-open Publication No. 4(1992)-345512, there has been proposed
a vehicle height control apparatus of the type which includes a set of fluid actuators
provided respectively at a pair of front road wheels and a pair of rear road wheels,
vehicle height sensors provided respectively at the front road wheels and a rear portion
of the vehicle body, and control means for controlling fluid under pressure supplied
to and discharged from the hydraulic actuators in accordance with each vehicle height
at the road wheels detected by the sensors to adjust the vehicle height to a predetermined
height. In the vehicle height control apparatus, the fluid actuators are communicated
to each other for a predetermined period of time immediately after adjustment of the
vehicle height to eliminate a difference in pressure therein. Such control of the
fluid actuators is effective to equalize vertical movements or rolling of the vehicle
body at the left and right road wheels during turning of the vehicle.
[0003] In the conventional vehicle height control apparatus, however, if the communication
between the fluid actuators is permitted in a condition where the vehicle is located
on an inclined or rough road or the vehicle is turning, accelerated or decelerated,
fluid under pressure in one of the fluid actuators applied with a large vertical load
flows into the other fluid actuator applied with a small vertical load. As a result,
the vehicle height at the road wheel applied with the large vertical load lowers while
the vehicle height at the road wheel applied with the small vertical load is raised.
It is, therefore, required to readjust the vehicle height. This means that the communication
between the fluid actuators is repeatedly permitted after readjustment of the vehicle,
resulting in the occurrence of a hunting phenomenon in adjustment of the vehicle height.
In addition, if each vehicle height at the road wheels is adjusted in a condition
where there is a large difference between vertical loads at the road wheels, the hunting
phenomenon in adjustment of the vehicle height will occur.
[0004] In view of the problems discussed above, a primary object of the present invention
is directed to provide a vehicle height control apparatus capable of eliminating a
hunting phenomenon in adjustment of each vehicle height at a set of road wheels.
[0005] According to the present invention, the object is accomplished by providing a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, first detection means
for detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
first detection means in such a manner that each vehicle height at the road wheels
is adjusted to a predetermined height, wherein the vehicle height control apparatus
comprises second detection means for detecting each vertical load at the road wheels,
and communication control means for effecting a communication between the fluid actuators
for a predetermined period of time after adjustment of each vehicle height at the
road wheels when a difference between the vertical loads detected by the second detection
means is smaller than a predetermined value.
[0006] According to a first aspect of the present invention, there is provided a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, first detection means
for detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
first detection means in such a manner that each vehicle height at the road wheels
is adjusted to a predetermined height, wherein the vehicle height control apparatus
comprises second detection means for detecting the fact that the vehicle is traveling
on a flat road, and communication control means for permitting a communication between
the fluid actuators for a predetermined period of time when it is detected by the
second detection means that the vehicle is traveling on a flat road after adjustment
of each vehicle height at the road wheels.
[0007] According to a second aspect of the present invention, there is provided a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, detection means for
detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
detection means in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height, wherein the vehicle height control apparatus comprises
communication control means for permitting a communication between the fluid actuators
for a predetermined period of time when a difference between vehicle heights detected
by the detection means after adjustment of each vehicle height at the road wheels
is smaller than a predetermined value.
[0008] According to a third aspect of the present invention, there is provided a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, detection means for
detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
detection means in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height, wherein the vehicle height control apparatus comprises
travel detection means for detecting the fact that the vehicle is traveling, and communication
control means for permitting a communication between the fluid actuators for a predetermined
period of time when it is detected by the travel detection means that the vehicle
is traveling after adjustment of each vehicle height at the road wheels.
[0009] According to a fourth aspect of the present invention, there is provided a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, detection means for
detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
detection means in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height, wherein the vehicle height control apparatus comprises
travel detection means for detecting the fact that the vehicle is turning, and communication
control means for permitting a communication between the fluid actuators for a predetermined
period of time when it is not detected by the travel detection means that the vehicle
is turning after adjustment of each vehicle height at the road wheels.
[0010] According to a fifth aspect of the present invention, there is provided a vehicle
height control apparatus adapted to a suspension system of an automotive vehicle including
a plurality of fluid actuators disposed between a body structure of the vehicle and
a set of road wheels for adjusting each vehicle height at the road wheels in accordance
with fluid pressure applied thereto, fluid control means for controlling fluid under
pressure supplied to and discharged from the fluid actuators, detection means for
detecting each vehicle height at the road wheels, and vehicle height control means
for controlling the fluid control means based on each vehicle height detected by the
detection means in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height, wherein the vehicle height control apparatus comprises
operation detection means for detecting a driver's operation causing vertical movement
of the vehicle body at at least one of the road wheels, and communication control
means for permitting a communication between the fluid actuators for a predetermined
period of time when it is not detected by the operation detection means that the vehicle
body is vertically moved at a portion thereof after adjustment of each vehicle height
at the road wheels.
[0011] For a better understanding of the present invention, and to show how the same may
be carried into effect, reference will now be made, by way of example, to the accompanying
drawings, in which:
Fig. 1 is a schematic illustration of a vehicle height control apparatus in accordance
with the present invention;
Fig. 2 is a flow chart of a control program executed by a microcomputer shown in Fig.
1;
Fig. 3 is a flow chart of a front side communication control routine shown in Fig.
2;
Fig. 4 is a flow chart of a rear side communication control routine shown in Fig.
2;
Fig. 5 is a flow chart of a modification of the control program shown in Fig. 2;
Fig. 6 is a flow chart of a communication control routine respectively shown in Figs.
3 and 4;
Fig. 7 is a flow chart of a modification of the communication control routine shown
in Fig. 6;
Fig. 8 is a flow chart of another modification of the control program shown in Fig.
2;
Fig. 9 is a flow chart of a modification of the program shown in Fig. 8; and
Fig. 10 is a flow chart of a further modification of the control program shown in
Fig. 2.
[0012] Illustrated in Fig. 1 of the drawings is a vehicle height control apparatus adapted
to a suspension system of an automotive vehicle which includes suspension devices
provided respectively at a pair of front road wheels and a pair of rear road wheels.
The suspension devices are composed of hydraulic dampers 11a-11d and pneumatic actuators
12a-12d, respectively. The hydraulic dampers 11a-11d cooperate with the pneumatic
actuators 12a-12d to support a body structure of the vehicle at the front and rear
road wheels. The pneumatic actuators 12a-12d act to effect vertical movements of the
vehicle body structure in accordance with pressure of the air supplied thereto. The
pneumatic actuators 12a-12d are connected in common to a compressor 14 through electromagnetic
valves 13a-13d which are switched over under control of a microcomputer 20 to selectively
establish each communication between the pneumatic actuators 12a and 12b and between
the pneumatic actuators 12c and 12d. The compressor 14 is driven by an electric motor
15 under control of the computer 20. An electromagnetic valve 16 is disposed within
a common conduit connecting the discharge port of compressor 14 to the electromagnetic
valves 13a-13d. The electromagnetic value 16 is switched over under control of the
computer 20 to selectively connect the common conduit to the atmospheric air.
[0013] The microcomputer 20 is programmed to execute a control program shown by flow charts
in Figs. 2 to 4. The computer 20 is connected to vehicle height sensors 21a-21d, pressure
sensors 22a-22d, load sensors 23a-23d, vertical acceleration sensors 24a-24d, a vehicle
speed sensor 25, a lateral acceleration sensor 26 and a steering angle sensor 27.
The vehicle height sensors 21a-21d are respectively assembled within the suspension
devices to detect each vehicle height H1-H4 at the front and rear road wheels for
producing detection signals indicative of the detected vehicle heights H1-H4. The
pressure sensors 22a-22d are respectively assembled within the pneumatic actuators
12a-12d to detect each air pressure P1-P4 in the pneumatic actuators 12a-12d for producing
detection signals respectively indicative of the detected air pressure P1-P4. The
load sensors 23a-23d are respectively disposed between the vehicle body structure
and the upper surfaces of pneumatic actuators 12a-12d to detect each load W1-W4 at
the road wheels for producing detection signals indicative of the detected loads W1-W4.
The vertical acceleration sensors 24a-24d are mounted on the vehicle body structure
to detect each vertical acceleration G1-G4 at the road wheels for producing detection
signals indicative of the detected vertical acceleration G1-G4. The vehicle speed
sensor 25 is mounted on the vehicle body structure to detect a travel speed V of the
vehicle for producing a detection signal indicative of the detected travel speed V.
The lateral acceleration sensor 26 is mounted on the vehicle body structure to detect
lateral acceleration Gy of the vehicle body for producing a detection signal indicative
of the detected lateral acceleration Gy. The steering angle sensor 27 is mounted on
a steering shaft assembly to detect a steering angle θ of a steering wheel for producing
a detection signal indicative of the detected steering angle θ. The steering angle
θ represents a neutral position of the steering wheel with "0" and represents leftward
or rightward steerage of the steering wheel with a positive or negative value.
[0014] In operation of the vehicle height control apparatus, the computer 20 starts to execute
the control program shown by flow charts in Fig. 2 to 4 at step 100 and sets at step
102 flags FLG 11 and FLG 12 indicative of vehicle height adjustment at the road wheels
respectively as "0". After initialization of the flags FLG 11 and FLG 12 at step 102,
the computer 20 reads out at step 104 each actual vehicle height H1-H4 detected by
the vehicle height sensors 21a-21d and determines whether all the actual vehicle heights
H1-H4 each are approximately equal to a predetermined standard height H0 or not. In
this embodiment, when the detected vehicle heights H1-H4 are in an extent between
a lower limit height H0 - ΔH and an upper limit height H0 + ΔH, it is presumed that
the detected vehicle heights are substantially equal to the standard height H0. When
the detected vehicle heights H1-H4 are lower than the lower limit height H0 - ΔH or
higher than the upper limit height H0 + ΔH, it is presumed that the detected vehicle
heights H1-H4 are lower than or higher than the standard vehicle height H0.
[0015] If the answer at step 104 is "Yes", the computer 20 determines a "No" answer at step
118 and returns the program to step 104. Thus, the computer 20 repeats execution of
processing at step 104 and 118 unless either one of the detected vehicle heights H1-H4
becomes lower or higher than the standard height H0. When either one of the detected
vehicle heights H1-H4 becomes lower or higher than the standard vehicle height H0
due to unloading or loading of burden, the computer 20 determines "No" answer at step
104 and causes the program to proceed to step 106-110. Processing at step 106-110
is executed by the computer 20 to memorize the vehicle heights H1-H4, air pressures
P1-P4 and loads W1-W4 detected before adjustment of the vehicle height. That is to
say, the computer 20 reads out vehicle heights H1-H4, air pressures P1-P4 and loads
W1-W4 detected by the vehicle height sensors 21a-21d, pressure sensors 22a-22d and
load sensors 23a-23d and memorizes the read out data as vehicle height data H1m-H4m,
air pressure data P1m-P4m and load data W1m-W4m.
[0016] After processing at step 106-110, the computer 20 acts at step 112 to independently
adjust each vehicle height H1-H4 at the front and rear road wheels to the standard
height H0. If in this instance, the vehicle height H1 (or H2-H4) at one of the road
wheels is lower than the standard height H0, the computer 20 activates the electric
motor 15 to drive the compressor 14 and switches over the electromagnetic valve 13a
(or 13b-134) from a first position shown in the figure to a second position. Thus,
the air discharged from the compressor 14 is supplied to the pneumatic actuator 12a
(or 12b-12d) through the electromagnetic valve 13a so that the air pressure in the
pneumatic actuator 12a (or 12b-12d) is increased to raise the vehicle height at the
road wheel. When the vehicle height H1 (or H2-H4) at the road wheel becomes substantially
equal to the standard height H0, the computer 20 deactivates the electric motor 15
and switches over the electromagnetic valve 13a (or 13b-13d) to the first position
shown in the figure. If the vehicle height H1 (or H2-H4) at one of the road wheels
is higher than the standard height H0, the computer 20 switches over the electromagnetic
valve 16 from a first position shown in the figure to a second position and switches
over the electromagnetic valve 13a (or 13b-13d) from the first position to the second
position. Thus, the air in the pneumatic actuator 12a (or 12b-12d) is discharged into
the atmospheric air through the electromagnetic valves 13a (or 13b-13d) and 16 to
lower the vehicle height H1 at the road wheel. When the vehicle height H1 detected
by the vehicle height sensor 21a (or 21b-21d) at the road wheel becomes substantially
equal to the standard height H0, the computer 20 switches over the electromagnetic
valves 13a (or 13b-13d) and 16 to their first positions.
[0017] In such a manner as described above, the vehicle heights H1-H4 are independently
adjusted in sequence. In this instance, the order of the vehicle heights to be adjusted
is preliminarily determined. For example, the vehicle heights are adjusted in a higher
order than the standard height H0 and adjusted in a lower order than the standard
height H0. Alternatively, each vehicle height at the front road wheels may be adjusted
after adjustment of each vehicle height at the rear road wheels. When all the vehicle
heights H1-H4 become substantially equal to the standard height H0 by processing at
step 112, the computer 20 determines a "Yes" answer at step 114 and returns the program
to step 104 after set the flags FLG 11 and FLG 12 to "1".
[0018] Thereafter, the computer 20 determines a "Yes" answer respectively at step 104 and
118 and causes the program to proceed to step 120-124. Thus, only when determined
a "Yes" answer respectively at step 120, 122 and 124, the computer 20 executes processing
at step 126 for permitting a communication between the pneumatic actuators 12a and
12b at the front road wheels and executes processing at step 128 for permitting a
communication between the pneumatic actuators 12c and 12d at the rear road wheels.
If a "No" answer is determined respectively at step 120, 122 or 124, the computer
20 returns the program to step 104.
[0019] At step 120, the computer 20 determines whether a travel speed V of the vehicle detected
by sensor 25 is higher than a predetermined speed V0 or not. If the answer at step
120 is "Yes", the computer 20 causes the program to proceed to step 122. If the answer
at step 120 is "No", the computer 20 returns the program to step 104. The processing
at step 120 is executed to determine whether the vehicle is stopping or traveling.
As vertical loads at the left and right road wheels become approximately equal to
each other during travel of the vehicle on a flat road, each communication between
the pneumatic actuators 12a and 12b and between the actuators 12c and 12d does not
cause any difference between the vehicle heights at the left and right road wheels.
This is useful to avoid readjustment of each vehicle height at the left and right
road wheels.
[0020] At step 122, the computer 20 determines whether an absolute value of a steering angle
θ detected by sensor 27 is smaller than a predetermined steering angle θ0 or not.
If the answer at step 122 is "Yes", the computer 20 causes the program to proceed
to step 124. If the answer at step 122 is "No", the computer 20 returns the program
to step 104. The processing at step 122 is executed to determine operation of a driver
causing vibration of the vehicle body and to determine a turning condition of the
vehicle. As vertical loads at the left and right road wheels become approximately
equal to each other during straight travel of the vehicle, each communication between
the pneumatic actuators 12a and 12b and between the pneumatic actuators 12c and 12d
does not cause any difference between the vehicle heights at the left and right road
wheels. This is useful to avoid readjustment of each vehicle height at the left and
right road wheels.
[0021] At step 124, the computer 20 determines whether an absolute value of lateral acceleration
Gy detected by sensor 26 is smaller than a predetermined value Gy0 or not. If the
answer at step 124 is "Yes", the computer 20 causes the program to proceed to step
126. If the answer at step 124 is "No", the computer 20 returns the program to step
104. The processing at step 124 is executed to indirectly determine the driver's operation
causing vibration of the vehicle body and to determine a turning condition of the
vehicle. As vertical loads at the left and right road wheels become approximately
equal to each other during straight travel of the vehicle, each communication between
the pneumatic actuators 12a and 12b and between the pneumatic actuators 12c and 12d
does not cause any difference between the vehicle heights at the left and right road
wheels. This is useful to avoid readjustment of each vehicle height at the left and
right road wheels.
[0022] The processing at step 126 for permitting a communication between the pneumatic actuators
12a and 12b at the front road wheels is executed as shown by the flow chart in Fig.
3. When a "Yes" answer is determined at step 124, the computer 20 starts at step 200
to execute a front side communication control routine for the processing at step 126
and determines at step 202 whether the flag FLG 11 is "1" or not. As the flag FLG
11 is set as "1" by processing at step 116 after adjustment of the vehicle heights
at the front road wheels, the computer 20 determines a "Yes" answer at step 202 and
causes the program to proceed to step 204-214. The processing at step 204-214 is executed
for control of the communication between the pneumatic actuators 12a and 12b at the
front road wheels. If a "Yes" answer is determined respectively at step 202-214, the
computer 20 executes processing at step 216 for permitting the communication between
pneumatic actuators 12a and 12b. If a "No" answer is determined at either one of steps
202-214, the computer 20 finishes at step 220 the execution of the front side communication
control routine.
[0023] At step 204, the computer 20 determines whether an absolute value of a difference
between air pressures P1 and P2 detected by sensors 22a and 22b at the front road
wheels is smaller than a predetermined value ΔPf0 or not. At step 206, the computer
20 determines whether an absolute value of a difference between loads W1 and W2 detected
by sensor 23a and 23b at the front road wheels is smaller than a predetermined value
ΔWf0 or not. At step 208, the computer 20 determines whether an absolute value of
a difference between the vehicle heights H1 and H2 detected by sensors 21a and 21b
at the front road wheels is smaller than a predetermined value ΔHf0 or not. If a "Yes"
answer is determined respectively at step 204-208, the computer 20 causes the program
to proceed to step 210-216.
[0024] The processing at step 204 and 206 is executed to directly determine whether vertical
loads at the front road wheels after adjustment of the vehicle height are equal to
each other or not. In this determination, the fact that each absolute value of the
differences between air pressures P1 and P2 and between loads W1 and W2 is smaller
than the predetermined values ΔPf0, ΔWf0 means that vertical loads at the front road
wheels are approximately equal to each other. The processing at step 208 is executed
to indirectly determine whether vertical loads at the front road wheels after adjustment
of the vehicle height are equal to each other or not. The fact that the absolute value
of the difference between the vehicle heights H1 and H2 is smaller than the predetermined
value ΔHf0 means that vertical loads at the front road wheels are approximately equal
to each other. Thus, even if the communication between the pneumatic actuators 12a
and 12b was permitted in a condition where vertical loads at the front road wheels
are equal to each other, any difference between the vehicle heights at the front road
wheels would not occur.
[0025] At step 210, the computer 20 determines whether an absolute value of a difference
between the memorized vehicle height data H1m and H2m is smaller than a predetermined
value ΔHmf0 or not. At the following step 212, the computer 20 determines whether
an absolute value of a difference between the memorized air pressure data P1m and
P2m is smaller than a predetermined value ΔPmf0 or not. At step 214, the computer
20 determines whether an absolute value of a difference between the memorized load
data W1m and W2m is smaller than a predetermined value ΔWmf0 or not. If a "Yes" answer
is determined respectively at step 210, 212 and 214, the computer 20 causes the program
to proceed to step 216. If a "No" answer is determined respectively at step 210, 212
and 214, the computer 20 causes the program to proceed to step 220.
[0026] The processing at step 210-214 is executed to determine whether the vertical loads
at the front road wheels before adjustment of the vehicle height were different in
a great amount or not. In this determination, the fact that each absolute value of
the differences between the memorized vehicle height data H1m and H2m, between the
memorized air pressure data P1m and P2m and between the memorized load data W1m and
W2m is smaller than the predetermined values ΔHmf0, ΔPmf0 and ΔWmf0 means that vertical
loads each at the front road wheels are approximately equal to each other. Thus, even
if the communication between the pneumatic actuators 12a and 12b was permitted in
a condition where vertical loads at the front road wheels are approximately equal
to each other, any difference between the vehicle heights at the front road wheels
would not occur.
[0027] When a "Yes" answer is determined respectively at step 202-214, the computer 20 switches
over at step 216 the electromagnetic valves 13a and 13b to their second positions
and maintain them in their second positions for a predetermined period of time in
a condition where the electric motor 15 is deactivated and where the electromagnetic
valve 16 is retained in the first position. Upon lapse of the predetermined period
of time, the computer 20 returns the electromagnetic valves 13a and 13b to their first
positions. Thus, the pneumatic actuators 12a and 12b are communicated to each other
for the predetermined period of time so that the air pressure in the pneumatic actuators
12a and 12b becomes equal. After processing at step 216, the computer 20 resets the
flag FLG 11 to "0" at step 218. Thereafter, the computer 20 determines a "No" answer
at step 202, finishes the execution of the front side communication control routine
at step 220 and returns the program to step 128 shown in Fig. 2.
[0028] The processing at step 128 for permitting a communication between the pneumatic actuators
12c and 12d at the rear road wheels is executed as shown by the flow chart in Fig.
4. After processing at step 126, the computer 20 starts at step 230 to execute a rear
side communication control routine for the processing at step 128 and determines at
step 232 whether the flag FLG 12 is "1" or not. As the flag FLG 12 is set as "1" by
processing at step 116 after adjustment of the vehicle height at the rear road wheels,
the computer 20 determines a "Yes" answer at step 232 and causes the program to proceed
to step 234-248. The processing at step 234-248 is executed for control of the communication
between the pneumatic actuators 12c and 12d at the rear road wheels. If a "Yes" answer
is determined respectively at step 232-248, the computer 20 executes processing at
step 250 for permitting the communication between pneumatic actuators 12c and 12d.
If a "No" answer is determined at either one of steps 232-248, the computer 20 finishes
at step 254 execution of the rear side communication control routine.
[0029] The processing at step 234-248 is executed to determine whether vertical loads at
the rear road wheels after adjustment of the vehicle height are equal to each other
or not. At step 234, the computer 20 determines whether an absolute value of a difference
between air pressures P3 and P4 detected by sensors 22c and 22d at the rear road wheels
is smaller than a predetermined value ΔPr0 or not. At step 236, the computer 20 determines
whether an absolute value of a difference between loads W3 and W4 detected by sensors
23c and 23d at the rear road wheels is smaller than a predetermined value ΔWr0 or
not. At step 238, the computer 20 determines whether an absolute value of a difference
between the vehicle heights H3 and H4 detected by sensors 21c and 21d at the rear
road wheels is smaller than a predetermined value ΔHr0 or not.
[0030] The processing at step 240-244 is executed to determine whether vertical loads at
the rear road wheels before adjustment of the vehicle height were different in a great
amount or not. At step 240, the computer 20 determines whether an absolute value of
a difference between the memorized vehicle height data H3m and H4m is smaller than
a predetermined value ΔHmr0 or not. At the following step 242, the computer 20 determines
whether an absolute value of a difference between the memorized air pressure data
P3m and P4m is smaller than a predetermined value ΔPmr0 or not. At step 244, the computer
20 determines whether an absolute value of a difference between the memorized load
data W3m and W4m is smaller than a predetermined value ΔWmr0 or not.
[0031] Processing at step 246 and 248 is executed to determine a large input applied from
road surfaces. At step 246, the computer 20 reads out vertical acceleration data G1,
G2 detected by vertical acceleration sensors 24a, 24b at the front road wheels and
determines whether a sum of absolute values of the detected vertical acceleration
data G1, G2 is smaller than a predetermined value Gf0 or not. At step 248, the computer
20 reads out vehicle height data H1, H2 detected by vehicle height sensors 21a, 21b
at the front road wheels and determines whether a sum of absolute values of each difference
between the detected vehicle heights H1, H2 and the standard height H0 is smaller
than a predetermined value Hf0 or not. In this instance, the fact that the sum of
absolute values of the detected vertical acceleration data G1, G2 is smaller than
the predetermined value Gf0 and that the sum of absolute values of each difference
between the detected vehicle heights H1, H2 and the standard height H0 is smaller
than the predetermined value Hf0 means that the front road wheels may not be applied
with any large input from road surfaces during further travel of the vehicle. In such
a condition, even if the pneumatic actuators 12c and 12d were communication to each
other, any difference in vehicle height to be readjusted would not occur.
[0032] When a "Yes" answer is determined respectively at step 232-248, the computer 20 switches
over the electromagnetic valves 13c and 13d to their second positions and maintain
them in position for a predetermined period of time. Upon lapse of the predetermined
period of time, the computer 20 returns the electromagnetic valves 13c and 13d to
their first positions. Thus, the pneumatic actuators 12c and 12d are communicated
to each other for the predetermined period of time to equalize the air pressure therein.
After processing at step 250, the computer 20 resets at step 252 the flag FLG 12 to
"0", determines at step 232 a "No" answer at step 232 and returns at step 254 the
program to step 104 shown in Fig. 2. Thereafter, when the flags 11 or 12 are set as
"1", the computer 20 determines a "No" answer at step 118 and returns the program
to step 104.
[0033] From the above description, it will be understood that the communication between
the pneumatic actuators 12a and 12b is permitted only once when a "Yes" answer is
determined respectively at step 120-124 and 204-214 after adjustment of the vehicle
height at the front road wheels while the communication between the pneumatic actuators
12c and 12d is effected only one when the computer 20 determines a "Yes" answer respectively
at step 120-124 and 234-248 after adjustment of the vehicle height at the rear road
wheels. With such control of each communication between the pneumatic actuators 12a
and 12b and between the pneumatic actuators 12c and 12d, readjustment of the vehicle
height at the front and rear road wheels can be avoided when the load of the vehicle
is inclined, when the vehicle is stopping or traveling on inclined or rough road surfaces
or when the vehicle is turning. Particularly, the processing at step 120 is useful
to avoid readjustment of the vehicle height at the front and rear road wheels in a
simple manner. Accordingly, each communication between the pneumatic actuators 12a
and 12b and between the pneumatic actuators 12c and 12d is permitted to equalize the
air pressure in the pneumatic actuators 12a, 12b and 12c, 12d without causing readjustment
of the vehicle height at the front and rear road wheels. This is effective to equalize
vertical movements of the vehicle body at the front and rear road wheels during straight
travel of the vehicle and to equalize rolling of the vehicle body during turning of
the vehicle.
[0034] Although in the above embodiment, the air pressures P1-P4 and loads W1-W4 detected
immediately before adjustment of the vehicle height are memorized as the air pressure
data P1m-P4m and load data W1m-W4m by processing at step 106 and 108, air pressures
P1-P4 and loads W1-W4 detected during stopping of the vehicle may be memorized as
the air pressure data P1m-P4m and load data W1m-W4m by processing at step 130 and
132 shown by broken lines in Fig. 2. In such a case, the computer 20 permits each
communication between the pneumatic actuators 12a and 12b and between the pneumatic
actuators 12c and 12d only when a "Yes" answer is determined respectively at step
212, 214 shown in Fig. 3 and step 242, 244 shown in Fig. 4. In such a modification
of the control program, vertical loads at the front and rear road wheels after adjustment
of the vehicle height can be accurately detected even when the load on the vehicle
body is inclined by loading or unloading of burden during stopping of the vehicle.
[0035] In the above embodiment, the computer 20 may be further connected to a road surface
sensor 31 and a road surface switch 32 as shown by broken lines in Fig. 1. In such
a case, as shown in Fig. 5, processing at step 140 and 142 is added to the processing
at step 118-128 shown in Fig. 2. In this modification, the road surface sensor 31
is arranged to measure an inclination at the front and rear road wheels for detecting
the fact that the vehicle is traveling on a flat road surface. Alternatively, the
road surface sensor 31 may be stored in a navigation system to detect the fact that
the vehicle is traveling on a flat road surface. The road surface switch 32 is arranged
to be operated by a driver when it is recognized that the vehicle is traveling on
a flat road surface. Processing at step 140 is executed to determine whether a flat
road surface is being detected by the road surface sensor 31 or not. If the answer
at step 140 is "Yes", the computer 20 permits each communication between the pneumatic
actuators 12a, 12b and between the pneumatic actuators 12c, 12d by processing at step
126 and 128. Processing at step 142 is executed to determine whether or not the road
surface switch 32 has been operated after adjustment of the vehicle height at the
front and rear road wheels. If the answer at step 142 is "Yes", the computer 20 permits
each communication between the pneumatic actuators 12a, 12b and between the pneumatic
actuators 12c, 12d by processing at step 126 and 128. In this modification, it is
preferable that an indication lamp or a buzzer to be activated after processing at
step 112 and 114 for adjustment of the vehicle height is provided to urge the driver
operation of the road surface switch 32. As in the modification, each communication
between the pneumatic actuators 12a, 12b and between the pneumatic actuators 12c,
12d is permitted under control of the computer 20 only when the vehicle is traveling
on a flat road surface after adjustment of the vehicle height, readjustment of the
vehicle height can be avoided.
[0036] Although in the embodiments described above, the pressure sensors 22a-22d have been
assembled within the pneumatic actuators 12a-12d respectively to detect the air pressure
in the pneumatic actuators 12a-12d, a single pressure sensor may be disposed in the
communication passage between the pneumatic actuators 12a, 12b and 12c, 12d to detect
the air pressure in the pneumatic actuators 12a-12d in sequence.
[0037] In a practical embodiment of the present invention, the processing at step 216 and
250 shown in Figs. 3 and 4 may be replaced with processing of a communication control
routine shown in Fig. 6. In this embodiment, the computer 20 starts at step 300 to
execute the communication control routine and sets at step 302 a timer stored therein
to measure a predetermined period of time during which the air pressure in pneumatic
actuators 12a and 12b and in pneumatic actuators 12c and 12d is equalized when the
pneumatic actuators 12a, 12b and 12c, 12d have been communicated to each other. The
timer is arranged to automatically count down the predetermined period of time when
applied with an instruction for permission of operation and to stop the count down
of the predetermined period of time when applied with an instruction for prohibition
of operation. After processing at step 302, the computer 20 determines at step 304
whether the vehicle is traveling on a rough road or not and determines at step 306
whether or not the vehicle body is vibrated at the front road wheels or the rear road
wheels.
[0038] At step 304, the computer 20 applies band-pass filter processing with a resonant
frequency (9 - 13 Hz) of a unsprung mass of the vehicle to each vehicle height H1-H4
at the front and rear road wheels detected by sensors 21a-21d to detect the variation
magnitude of each vehicle height at the front and rear road wheels. When an average
of the variation magnitude of each vehicle height at the front and rear road wheels
is larger than a predetermined value, it is determined by the computer 20 that the
vehicle is traveling on a rough road. Alternatively, the computer 20 may be arranged
to apply the same processing as described above to vertical acceleration data G1-G4
detected by vertical acceleration sensors 24a-24d and to an integrated or differentiated
value of the same data. When an average of the variation magnitude of the vertical
acceleration data G1-G4 or the integrated or differentiated value of the same data
becomes larger than a predetermined value, it is determined by the computer 20 that
the vehicle is traveling on a rough road.
[0039] At step 306, the computer 20 reads out each vehicle height H1, H2 at the front road
wheels detected by sensors 21a, 21b (or each vehicle height H3, H4 at the rear road
wheels detected by sensors 21c, 21d) to calculate a difference between the vehicle
height data H1 and H2 (or the vehicle height data H3 and H4) and applies low-pass
or band-pass filter processing to the calculated difference between the vehicle height
data H1 and H2 (or vehicle height data H3 and H4). When the calculated difference
between the vehicle height data H1 and H2 (or the vehicle height data H3 and H4) becomes
larger than a predetermined value, it is determined by the computer 20 that the vertical
vibration of the vehicle body at the front road wheels (or at the rear road wheels)
is large.
[0040] When the vertical vibration of the vehicle body at the front or rear road wheels
is small during travel of the vehicle on a flat road, the computer 20 determines a
"No" answer respectively at step 304 and 306, switches over at step 308 the electromagnetic
valves 13a, 13b (or 13c, 13d) to their second positions to effect a communication
between the pneumatic actuators 12a and 12b (or the pneumatic actuators 12c and 12d),
and causes at step 310 the timer to count down the predetermined period of time. Thus,
the communication between the pneumatic actuators 12a and 12b (or the pneumatic actuators
12c and 12d) is maintained for the predetermined time during which the computer 20
repeats execution of processing at step 304-310 and 316.
[0041] When the vehicle starts to travel on a rough road, the vertical vibration of the
vehicle body at the front road wheels (or at the rear road wheels) becomes large.
In such an instance, the computer 20 determines a "Yes" answer at step 304 or 306,
returns the electromagnetic valves 13a, 13b (or 13c, 13d) to their first positions
at step 312 to interrupt the communication between the pneumatic actuators 12a and
12b (or 12c and 12d), and causes the timer at step 314 to stop the count down of the
predetermined period of time. Thereafter, if the vehicle is still traveling on the
rough road, the computer repeats execution of processing at step 304, 312 and 314.
[0042] Upon lapse of the predetermined period of time set by processing at step 302, the
computer 20 determines a "Yes" answer at step 316, returns the electromagnetic valves
13a, 13b (or 13c, 13d) to their first positions at step 318 to interrupt the communication
between the pneumatic actuators 12a and 12b (or 12c and 12d) and finishes execution
of the communication control routine at step 320.
[0043] As is understood from the above description, the communication between the pneumatic
actuators 12a and 12b (or 12c and 12d) is prohibited when the vertical vibration of
the vehicle body at the front road wheels (or at the rear road wheels) becomes large
and is permitted only when the vertical vibration of the vehicle body at the front
road wheels (or at the rear road wheels) is small during travel of the vehicle on
a flat road surface. As a result, the communication between the pneumatic actuators
12a and 12b (or 12c and 12d) is maintained only for the predetermined period of time
in a condition where there is not any large variation of air pressure in the pneumatic
actuators 12a and 12b (or 12c and 12d). This is useful to more accurately equalize
the air pressure in the pneumatic actuators 12a and 12b (or 12c and 12d.
[0044] The communication control routine shown in Fig. 6 may be replaced with a communication
control routine shown in Fig. 7. In this modification, the computer 20 starts at step
330 to execute the communication control routine and switches over at step 332 the
electromagnetic valves 13a and 13b (or 13c and 13d) to their second positions to permit
a communication between the pneumatic actuators 12a and 12b (or 12c and 12d) and to
maintain the communication between the pneumatic actuators 12a and 12b (or 12c and
12d) for a predetermined period of time. Upon lapse of the predetermined period of
time, the program proceeds to step 334 where the computer 20 reads out each vehicle
height H1 and H2 detected by sensors 21a and 21b (or each vehicle height H3 and H4
detected by sensors 21c and 21d) and determines whether an absolute value of a difference
between the vehicle height data H1 and H2 (or H3 and H4) is less than a predetermined
small value or not. If the answer at step 334 is "Yes", the computer 20 returns the
electromagnetic valves 13a and 13b (or 13c and 13d) to their first positions at step
336 to interrupt the communication between the pneumatic actuators 12a and 12b (or
12c and 12d) and finishes at step 338 execution of the communication control routine.
If the answer at step 334 is "No", the computer 20 repeats execution of processing
at step 334 until the absolute value of the difference between the vehicle height
data H1 and H2 (or H3 and H4) becomes less than the predetermined small value.
[0045] As is understood from the above description, the communication between the pneumatic
actuators 12a and 12b (or12c and 12d) is maintained until the absolute value of the
difference between the vehicle heights H1 and H2 at the front road wheels (or between
the vehicle heights H3 and H4 at the rear road wheels) becomes less than the predetermined
small value. Accordingly, the communication between the pneumatic actuators 12a and
12b (or 12c and 12d) is interrupted only when the vehicle height data H1 and H2 at
the front road wheels (or the vehicle height data H3 and H4 at the rear road wheels)
become equal to each other. As a result, the air pressure in the pneumatic actuators
12a and the communication between the pneumatic actuators 12a and 12b (or 12c and
12d) is equalized when the communication between the pneumatic actuators 12a and 12b
(or 12c and 12d) is interrupted under control of the computer 20. This is useful to
accurately equalize vertical movements of the vehicle body at the left and right road
wheels caused by turning of the vehicle.
[0046] In the practical embodiment of the present invention, the computer 20 may be connected
to a door switch 33 and a trunk switch 34 as shown by broken lines in Fig. 1. The
door switch 33 is in the form of a normally closed type which is opened when a door
of the vehicle is opened, and the trunk switch 34 is in the form of a normally closed
type which is opened when a trunk of the vehicle is opened. In this embodiment, the
control program shown in Fig. 2 is modified as shown in Fig. 8.
[0047] When started at step 100 to execute the control program shown in Fig. 8, the computer
20 initializes at step 102a the flags FLG 11 and FLG 12 and a flag FLG 2 as "0", respectively.
When set as "1", the flag FLG 2 represents the fact that readjustment of the vehicle
height is required due to communication between the pneumatic actuators 12a and 12b
(and/or 12c and 12d) effected after adjustment of the vehicle height. After processing
at step 102a, the computer 20 determines at step 160 whether a door of the vehicle
or the trunk of the vehicle is opened during stopping of the vehicle or not. The processing
at step 160 is executed to detect a condition where a passenger is getting in and
out of the vehicle compartment or a burden is being loaded or unloaded. If the door
or trunk is opened during stopping of the vehicle, the computer 20 determines a "Yes"
answer at step 160 and resets the flag FLG 2 to "0" at step 162. If the door and trunk
are closed during travel of the vehicle, the computer 20 determines a "No" answer
at step 160 and causes the program to step 104.
[0048] When each vehicle height H1-H4 is approximately equal to the standard height H0 in
a condition where all the flags FLG 11, FLG 12 and FLG 2 each are maintained as "0",
the computer 20 determines a "Yes" answer respectively at step 104 and 164 and determines
a "No" answer at step 118 to repeat execution of processing at step 160, 162, 104,
164 and 118. When either one of the vehicle heights H1-H4 becomes lower or higher
than the standard height H0, the computer 20 determines a "No" answer at step 104
and executes processing at step 112 and 114 for adjustment of the vehicle height.
Thereafter, the computer 20 sets at step 116 the flags FLG 11 and FLG12 respectively
as "1" and determines a "Yes" answer at step 118. After adjustment of the vehicle
height, the communication between pneumatic actuators 12a and 12b (and/or 12c and
12d) is effected by processing at step 126 and 128, and the flags FLG 11 and FLG12
each are reset to "0".
[0049] Subsequently, the computer 20 determines a "Yes" answer at step 166 and causes the
program to proceed to step 168. At step 168, the computer 20 determines the following
facts 1) - 4) within a predetermined period of time after processing at step 126 and
128.
1) Whether only one of the vehicle heights H1 and H2 at the front road wheels was
displaced from the standard height H0 or not.
2) Whether only one of the vehicle heights H3 and H3 at the rear road wheels was displaced
from the standard height H0 or not.
3) Whether either one of the vehicle heights H1 and H2 at the front road wheels was
displaced in a reverse direction after adjusted by processing at step 126 or not.
4) whether either one of the vehicle heights H3 and H4 at the rear road wheels was
displaced in a reverse direction after adjusted by processing at step 128 or not.
[0050] The processing at step 168 is executed to detect a condition where the vehicle height
was displaced at either one of the front and rear road wheels due to the communication
between the pneumatic actuators 12a and 12b (or 12c and 12d) effected after adjustment
of the vehicle height.
[0051] If the answer at step 168 is "No", the computer 20 returns the program to step 160
to repeat execution of processing at step 160, 162, 104, 164 and 118. If the answer
at step 168 is "Yes", the computer 20 sets the flag FLG 2 to "1" and returns the program
to step 160. As in such an instance, at least one of the vehicle heights H1-H4 is
displaced from the standard height H0, the computer 20 determines a "No" answer at
step 104 after processing at step 160 and 162 to execute processing at step 112 and
114 for adjustment of the displaced vehicle height and sets the flags FLG 11 and FLG
12 to "1" at step 116. Thereafter, the computer 20 returns the program to step 160
to execute processing at step 160, 162, 104 and 164. In this instance, the computer
20 determines a "No" answer at step 164 as the flag FLG 2 is set as "1" by processing
at step 170 and returns the program to step 160 without executing processing at step
126 and 128 for effecting the communication between the pneumatic actuators 12a and
12b (or 12c and 12d). Thus, in a condition where the vehicle height was displaced
due to the communication between the Pneumatic actuators 12a and 12b (or 12c and 12d)
effected after adjustment of the vehicle height, the communication between the pneumatic
actuators 12a and 12b (or 12c and 12d) after readjustment of the vehicle height is
prohibited under control of the computer 20. This is useful to maintain the vehicle
heights at the front and rear road wheels approximately at the standard height H0.
[0052] If a door of the vehicle is opened during processing at step 160, 162, 104 and 164,
the computer 20 determines a "Yes" answer at step 160 and resets the flag FLG 2 to
"0" at step 162. In such an instance, the computer 20 determines a "Yes" answer at
step 164 and executes processing at step 126 and 128 for effecting the communication
between the pneumatic actuators 12a and 12b (and/or 12c and 12d). The processing at
step 126 and 128 is executed to eliminate inclination of the vehicle body caused by
passengers getting in and out of the vehicle compartment or burden loaded or unloaded
in a condition where the door or trunk is being opened. Although in this embodiment,
the processing at step 168 is executed to detect displacement of the vehicle height
caused by the communication between the pneumatic actuators 12a and 12b (and/or 12c
and 12d), the processing at step 168 may be executed as in the processing at step
104 to detect displacement of either one of the vehicle heights H1-H4. Although in
this embodiment, the flag FLG 2 is reset to "0" when the door or trunk of the vehicle
is opened during stopping of the vehicle, the flag FLG 2 may be reset to "0" when
passengers get in and out of the vehicle compartment or burden is loaded or unloaded.
In such a case, the processing at step 100-162 shown in Fig. 8 is modified as shown
in Fig. 9.
[0053] Assuming that the computer 20 has started to execute a control program shown in Fig.
9 at step 100, the flags FLG 11, FLG12, FLG2 and an additional flag FLG 3 each are
initialized as "0" at step 102b. After processing at step 102b, the computer 20 determines
at step 180 whether the vehicle is traveling or not. If the answer at step 180 is
"Yes", the computer 20 sets the flag FLG 3 as "1" at step 194 and causes the program
to proceed to step 104 shown in Fig. 8. If the vehicle is stopping after traveled,
the computer 20 determines a "No" answer at step 180 and determines a "Yes" answer
at step 182 to execute processing at step 184. As step 184, the computer 20 reads
out each vehicle height H1-H4 at the front and rear road wheels detected by sensors
21a-21d and memorizes them as vehicle height data H1n-H4n. Thereafter, the computer
20 resets the flag FLG 3 to "0" at step 186. If the flag FLG 3 is set as "0", the
computer 20 causes the program at step 182 to proceed to step 188 without executing
processing at step 184 and 186. Thus, the memorized vehicle height data H1n-H4n are
renewed by processing at step 180-186 and 194 only once immediately after the vehicle
has stopped.
[0054] When the vehicle is stopping, the computer 20 determines at step 188 whether a door
or trunk of the vehicle is opened or not and determines at step 190 whether the load
of the vehicle such as the number of passengers and burden has changed or not. In
processing as step 190, the computer 20 calculates each difference between the memorized
vehicle height data H1n-H4n and current vehicle height data H1-H4 detected by sensors
21a-21d and determines whether either one of the calculated differences is larger
than a predetermined value or not. Thus, only when either one of the calculated differences
is larger than the predetermined value in a condition where the door or trunk of the
vehicle is being opened, the computer 20 determines a "Yes" answer respectively at
step 188 and 190 and resets the flag FLG 2 to "0" at step 192. In other conditions,
the flag FLG 2 is maintained in a previous value.
[0055] In such control as described above, when the flag FLG 2 is set once as "1" by processing
at step 170 shown in Fig. 8, the flag FLG 2 is maintained as "1" until the load of
the vehicle changes in a condition where the door or trunk of the vehicle is being
opened. Thus, even if either one of the vehicle heights H1-H4 was adjusted after readjustment,
each communication between the pneumatic actuators 12a and 12b and between the pneumatic
actuators 12c and 12d would not be permitted. This is useful to avoid a hunting phenomenon
in adjustment of the vehicle height.
[0056] In another embodiment of the present invention, the computer 20 may be further connected
to an accelerator sensor 35, a brake switch 36 and a fore-and-aft acceleration sensor
37. The accelerator sensor 35 is arranged to detect an opening degree AC of a throttle
valve of an internal combustion engine of the vehicle for producing a detection signal
indicative of the opening degree AC of the throttle valve. The brake switch 36 is
in the form of a normally open switch to be closed by depression of a brake pedal
of the vehicle. The fore-and-aft acceleration sensor 37 is mounted on the vehicle
body structure to detect acceleration or deceleration of the vehicle for producing
a detection signal indicative of a fore-and-aft acceleration Gx of the vehicle. In
this embodiment, the control program shown in Figs. 2 to 4 is replaced with a control
program shown in Fig. 10.
[0057] Assuming that the computer 20 has started to execute the control program shown in
Fig. 10 at step 400, the computer 20 initializes at step 402 the flag FLG 1 to "0"
and causes the program to proceed to step 404. If each vehicle height H1-H4 detected
by sensors 21a-21d is approximately equal to the standard height H0, the computer
20 determines a "Yes" answer at step 404 and determines a "No" answer at step 412
to repeat execution of processing at step 404 and 412. If either one of the vehicle
heights H1-H4 is lower or higher than the standard height H0, the computer 20 determines
a "No" answer at step 404 and executes processing at step 406 and 408 for adjusting
the vehicle height to the standard height H0 in the same manner as in the processing
at step 104, 112 and 114 shown in Fig. 2. After adjustment of the vehicle height,
the computer 20 sets the flag FLG 1 to "1" and determines a "Yes" answer respectively
at step 404 and 412 to execute processing at step 414-418. The processing at step
414-418 is to determine whether the vehicle is traveling or not, to determine whether
an absolute value of a steering angle detected by sensor 27 is smaller than the predetermined
value θ0 or not, and to determine whether lateral acceleration Gy detected by sensor
26 is smaller than the predetermined value Gy0 or not.
[0058] When the program proceeds to step 420, the computer 20 reads out an opening degree
AC of the engine throttle detected by sensor 35 and determines whether the detected
opening degree AC is smaller than a predetermined opening degree AC0 or not. After
processing at step 420, the computer 20 determines at step 422 whether the brake switch
36 is closed or not and determines at step 424 whether fore-and-aft acceleration Gx
of the vehicle detected by sensor 37 is smaller than a predetermined value Gx0 or
not. If a "Yes" answer is determined respectively at step 414-424, the program proceeds
to step 426 where the computer 20 switches over the electromagnetic valves 13a-13d
to their second positions to effect each communication between the pneumatic actuators
12a and 12b and between the pneumatic actuators 12c and 12d and maintain the communication
between the pneumatic actuators 12a and 12b and between the pneumatic actuators 12c
and 12d for a predetermined period of time to equalize the air pressure in the pneumatic
actuators 12a, 12b and 12c, 12d. After processing at step 426, the computer 20 resets
the flag FLG 1 to "0" to repeat execution of processing at step 404 and 412.
[0059] As is understood from the above description, each communication between the pneumatic
actuators 12a and 12b and between the pneumatic actuators 12c and 12d is effected
only once when a "Yes" answer is determined respectively at step 414-424 after adjustment
of the vehicle height at step 406 and 408. The processing at step 414-424 is useful
to prohibit each communication between the pneumatic actuators 12a and 12b and between
the pneumatic actuators 12c and 12 in a condition where the vehicle is traveling on
a bumpy road or turning. With such control as described above, the air pressure in
the pneumatic actuators 12a, 12b and 12c, 12d is equalized without causing any displacement
of the adjusted vehicle heights at the front and rear road wheels. This is useful
to equalize rolling of the vehicle body during turning of the vehicle and to equalize
pitching of the vehicle body during acceleration or deceleration of the vehicle.
[0060] Although in the embodiment described above, the processing at step 426 is executed
to effect each communication between the pneumatic actuators 12a and 12b and between
the pneumatic actuators 12c and 12d after adjustment of the vehicle height, the processing
at step 426 may be modified to independently effect a communication between the pneumatic
actuators 12a and 12b and a communication between the pneumatic actuators 12c and
12d after adjustment of the vehicle height and to maintain the communications respectively
for a predetermined time.
1. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators (12a-12d), first detection means (21a-21d) for detecting
each vehicle height at the road wheels, and vehicle height control means (112, 114)
for controlling said fluid control means (13a-13d) based on each vehicle height detected
by said first detection means (21a-21d) in such a manner that each vehicle height
at the road wheels is adjusted to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
second detection means (23a-23d) for detecting each vertical load at the road wheels;
and
communication control means (126, 128) for effecting a communication between said
fluid actuators (12a-12d) for a predetermined period of time after adjustment of each
vehicle height at the road wheels when a difference between the vertical loads detected
by said second detection means (23a-23d) is smaller than a predetermined value.
2. A vehicle height control apparatus as claimed in Claim 1, wherein said communication
control means (126, 128) is arranged to effect the communication between said fluid
actuators for the predetermined period of time when a difference between vertical
loads detected by said second detection means (21a-21d) immediately before adjustment
of each vehicle height at the road wheels is smaller than the predetermined value.
3. A vehicle height control apparatus as claimed in Claim 1, wherein said communication
control means (126, 128) is arranged to effect the communication between said actuators
(12a-12d) for the predetermined period of time when a difference between vertical
loads detected by said second detection means (23a-23d) during stopping of the vehicle
is smaller than the predetermined value.
4. A vehicle height control apparatus as claimed in Claim 1, wherein said communication
control means (126, 128) is arranged to effect the communication between said actuators
(12a-12d) for the predetermined period of time when a difference between vertical
loads detected by said second detection means (23a-23d) after adjustment of each vehicle
height at the road wheels is smaller than the predetermined value.
5. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators (12a-12d), first detection means (21a-21d) for detecting
each vehicle height at the road wheels, and vehicle height control means (112, 114)
for controlling said fluid control means (13a-13d) based on each vehicle height detected
by said first detection means (21a-21d) in such a manner that each vehicle height
at the road wheels is adjusted to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
second detection means (120) for detecting the fact that the vehicle is traveling
on a flat road; and
communication control means (126, 128) for permitting a communication between said
fluid actuators (12a-12d) for a predetermined period of time when it is detected by
said second detection means (120) that the vehicle is traveling on a flat road after
adjustment of each vehicle height at the road wheels.
6. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators, detection means (21a-21d) for detecting each vehicle height
at the road wheels, and vehicle height control means (112, 114) for controlling said
fluid control means (13a-13d, 16) based on each vehicle height detected by said detection
means (21a-21d) in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
communication control means (126, 128) for permitting a communication between said
fluid actuators (12a-12d) for a predetermined period of time when a difference between
vehicle heights detected by said detection means (21a-21d) after adjustment of each
vehicle height at the road wheels is smaller than a predetermined value.
7. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators (12a-12d), detection means (21a-21d) for detecting each vehicle
height at the road wheels, and vehicle height control means (112, 114) for controlling
the fluid control means (13a-13d, 16) based on each vehicle height detected by said
detection means (21a-21d) in such a manner that each vehicle height at the road wheels
is adjusted to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
travel detection means (120) for detecting the fact that the vehicle is traveling;
and
communication control means (126, 128) for permitting a communication between said
fluid actuators (12a-12d) for a predetermined period of time when it is detected by
said travel detection means (120) that the vehicle is traveling after adjustment of
each vehicle height at the road wheels.
8. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators, detection means (21a-21d) for detecting each vehicle height
at the road wheels, and vehicle height control means 112, 114) for controlling the
fluid control means (13a-13d, 16)based on each vehicle height detected by said detection
means (21a-21d) in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
travel detection means (122) for detecting the fact that the vehicle is turning; and
communication control means (126, 128) for permitting a communication between said
fluid actuators (12a-12d) for a predetermined period of time when it is not detected
by said travel detection means (122) that the vehicle is turning after adjustment
of each vehicle height at the road wheels.
9. A vehicle height control apparatus adapted to a suspension system of an automotive
vehicle including a plurality of fluid actuators (12a-12d) disposed between a body
structure of the vehicle and a set of road wheels for adjusting each vehicle height
at the road wheels in accordance with fluid pressure applied thereto, fluid control
means (13a-13d, 16) for controlling fluid under pressure supplied to and discharged
from the fluid actuators, detection means (21a-21d) for detecting each vehicle height
at the road wheels, and vehicle height control means (112, 114) for controlling the
fluid control means (13a-13d, 16) based on each vehicle height detected by said detection
means (21a-21d) in such a manner that each vehicle height at the road wheels is adjusted
to a predetermined height (H0),
wherein the vehicle height control apparatus comprises:
operation detection means (306) for detecting a driver's operation causing vertical
movement of the vehicle body at at least one of the road wheels; and
communication control means (126, 128) for permitting a communication between said
fluid actuators (12a-12d) for a predetermined period of time when it is not detected
by said operation detection means (306) that the vehicle body is vertically moved
at a portion thereof after adjustment of each vehicle height at the road wheels.
10. A vehicle height control apparatus as claimed in Claim 1, further comprising:
means (312) for prohibiting the communication between said fluid actuators when the
vehicle body is vertically vibrated during traveling of the vehicle.
11. A vehicle height control apparatus as claimed in Claim 1, wherein said communication
control means (126, 128) includes means (334) for maintaining the communication between
said fluid actuators (12a-12d) until a difference between vehicle heights detected
by said detection means (21a-21d) becomes smaller than a predetermined value.
12. A vehicle height control apparatus as claimed in Claim 1, further comprising:
third detection means (168) for detecting displacement of each vehicle height at the
road wheels caused by the communication between said fluid actuators (12a-12d) within
a predetermined period of time; and
means (170) for prohibiting the communication between said fluid actuators (12a-12d)
when it is detected by said third detection means (168) that either one of vehicle
heights at the road wheels was displaced after readjustment of the vehicle height.